The present invention relates to a test indicator used for comparative measurement.
The test indicator is a conventional instrument which has been used for measuring a narrow spot, a deep place where a dial gauge cannot reach, the inner diameter of a hole, or the outer diameter of a shaft. The working principle is usually such that the displacement of a measuring member or tip of a measuring arm pivoted to the casing is transmitted by an axially slidable intermediate shaft within the casing to a built-in magnifying means in the casing so that the displacement can be indicated with magnification on the dial scale. The measuring arm, however, can pivot only in opposite directions in a single plane perpendicular to its pivot shaft and accordingly, depending on the place to be measured, the dial scale is turned and becomes obscured to the operator. In that case the operator has to peer around into the dial scale, thereby making the measurement inefficient.